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[Docs] Update JSON functions docs
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docs/en/sql-reference/functions/json-functions.md
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@ -4,13 +4,13 @@ sidebar_position: 105
sidebar_label: JSON
---
There are two sets of functions to parse JSON.
- `simpleJSON*` (`visitParam*`) is made to parse a special very limited subset of a JSON, but these functions are extremely fast.
- `JSONExtract*` is made to parse normal JSON.
There are two sets of functions to parse JSON:
- [`simpleJSON*` (`visitParam*`)](#simplejson--visitparam-functions) which is made for parsing a limited subset of JSON extremely fast.
- [`JSONExtract*`](#jsonextract-functions) which is made for parsing ordinary JSON.
# simpleJSON/visitParam functions
## simpleJSON / visitParam functions
ClickHouse has special functions for working with simplified JSON. All these JSON functions are based on strong assumptions about what the JSON can be, but they try to do as little as possible to get the job done.
ClickHouse has special functions for working with simplified JSON. All these JSON functions are based on strong assumptions about what the JSON can be. They try to do as little as possible to get the job done as quickly as possible.
The following assumptions are made:
@ -19,7 +19,7 @@ The following assumptions are made:
3. Fields are searched for on any nesting level, indiscriminately. If there are multiple matching fields, the first occurrence is used.
4. The JSON does not have space characters outside of string literals.
## simpleJSONHas
### simpleJSONHas
Checks whether there is a field named `field_name`. The result is `UInt8`.
@ -29,14 +29,16 @@ Checks whether there is a field named `field_name`. The result is `UInt8`.
simpleJSONHas(json, field_name)
```
Alias: `visitParamHas`.
**Parameters**
- `json`: The JSON in which the field is searched for. [String](../data-types/string.md#string)
- `field_name`: The name of the field to search for. [String literal](../syntax#string)
- `json` — The JSON in which the field is searched for. [String](../data-types/string.md#string)
- `field_name` — The name of the field to search for. [String literal](../syntax#string)
**Returned value**
It returns `1` if the field exists, `0` otherwise.
- Returns `1` if the field exists, `0` otherwise. [UInt8](../data-types/int-uint.md).
**Example**
@ -55,11 +57,13 @@ SELECT simpleJSONHas(json, 'foo') FROM jsons;
SELECT simpleJSONHas(json, 'bar') FROM jsons;
```
Result:
```response
1
0
```
## simpleJSONExtractUInt
### simpleJSONExtractUInt
Parses `UInt64` from the value of the field named `field_name`. If this is a string field, it tries to parse a number from the beginning of the string. If the field does not exist, or it exists but does not contain a number, it returns `0`.
@ -69,14 +73,16 @@ Parses `UInt64` from the value of the field named `field_name`. If this is a str
simpleJSONExtractUInt(json, field_name)
```
Alias: `visitParamExtractUInt`.
**Parameters**
- `json`: The JSON in which the field is searched for. [String](../data-types/string.md#string)
- `field_name`: The name of the field to search for. [String literal](../syntax#string)
- `json` — The JSON in which the field is searched for. [String](../data-types/string.md#string)
- `field_name` — The name of the field to search for. [String literal](../syntax#string)
**Returned value**
It returns the number parsed from the field if the field exists and contains a number, `0` otherwise.
- Returns the number parsed from the field if the field exists and contains a number, `0` otherwise. [UInt64](../data-types/int-uint.md).
**Example**
@ -98,6 +104,8 @@ INSERT INTO jsons VALUES ('{"baz":2}');
SELECT simpleJSONExtractUInt(json, 'foo') FROM jsons ORDER BY json;
```
Result:
```response
0
4
@ -106,7 +114,7 @@ SELECT simpleJSONExtractUInt(json, 'foo') FROM jsons ORDER BY json;
5
```
## simpleJSONExtractInt
### simpleJSONExtractInt
Parses `Int64` from the value of the field named `field_name`. If this is a string field, it tries to parse a number from the beginning of the string. If the field does not exist, or it exists but does not contain a number, it returns `0`.
@ -116,14 +124,16 @@ Parses `Int64` from the value of the field named `field_name`. If this is a stri
simpleJSONExtractInt(json, field_name)
```
Alias: `visitParamExtractInt`.
**Parameters**
- `json`: The JSON in which the field is searched for. [String](../data-types/string.md#string)
- `field_name`: The name of the field to search for. [String literal](../syntax#string)
- `json` — The JSON in which the field is searched for. [String](../data-types/string.md#string)
- `field_name` — The name of the field to search for. [String literal](../syntax#string)
**Returned value**
It returns the number parsed from the field if the field exists and contains a number, `0` otherwise.
- Returns the number parsed from the field if the field exists and contains a number, `0` otherwise. [Int64](../data-types/int-uint.md).
**Example**
@ -145,6 +155,8 @@ INSERT INTO jsons VALUES ('{"baz":2}');
SELECT simpleJSONExtractInt(json, 'foo') FROM jsons ORDER BY json;
```
Result:
```response
0
-4
@ -153,7 +165,7 @@ SELECT simpleJSONExtractInt(json, 'foo') FROM jsons ORDER BY json;
5
```
## simpleJSONExtractFloat
### simpleJSONExtractFloat
Parses `Float64` from the value of the field named `field_name`. If this is a string field, it tries to parse a number from the beginning of the string. If the field does not exist, or it exists but does not contain a number, it returns `0`.
@ -163,14 +175,16 @@ Parses `Float64` from the value of the field named `field_name`. If this is a st
simpleJSONExtractFloat(json, field_name)
```
Alias: `visitParamExtractFloat`.
**Parameters**
- `json`: The JSON in which the field is searched for. [String](../data-types/string.md#string)
- `field_name`: The name of the field to search for. [String literal](../syntax#string)
- `json` — The JSON in which the field is searched for. [String](../data-types/string.md#string)
- `field_name` — The name of the field to search for. [String literal](../syntax#string)
**Returned value**
It returns the number parsed from the field if the field exists and contains a number, `0` otherwise.
- Returns the number parsed from the field if the field exists and contains a number, `0` otherwise. [Float64](../data-types/float.md/#float32-float64).
**Example**
@ -192,6 +206,8 @@ INSERT INTO jsons VALUES ('{"baz":2}');
SELECT simpleJSONExtractFloat(json, 'foo') FROM jsons ORDER BY json;
```
Result:
```response
0
-4000
@ -200,7 +216,7 @@ SELECT simpleJSONExtractFloat(json, 'foo') FROM jsons ORDER BY json;
5
```
## simpleJSONExtractBool
### simpleJSONExtractBool
Parses a true/false value from the value of the field named `field_name`. The result is `UInt8`.
@ -210,10 +226,12 @@ Parses a true/false value from the value of the field named `field_name`. The re
simpleJSONExtractBool(json, field_name)
```
Alias: `visitParamExtractBool`.
**Parameters**
- `json`: The JSON in which the field is searched for. [String](../data-types/string.md#string)
- `field_name`: The name of the field to search for. [String literal](../syntax#string)
- `json` — The JSON in which the field is searched for. [String](../data-types/string.md#string)
- `field_name` — The name of the field to search for. [String literal](../syntax#string)
**Returned value**
@ -240,6 +258,8 @@ SELECT simpleJSONExtractBool(json, 'bar') FROM jsons ORDER BY json;
SELECT simpleJSONExtractBool(json, 'foo') FROM jsons ORDER BY json;
```
Result:
```response
0
1
@ -247,7 +267,7 @@ SELECT simpleJSONExtractBool(json, 'foo') FROM jsons ORDER BY json;
0
```
## simpleJSONExtractRaw
### simpleJSONExtractRaw
Returns the value of the field named `field_name` as a `String`, including separators.
@ -257,14 +277,16 @@ Returns the value of the field named `field_name` as a `String`, including separ
simpleJSONExtractRaw(json, field_name)
```
Alias: `visitParamExtractRaw`.
**Parameters**
- `json`: The JSON in which the field is searched for. [String](../data-types/string.md#string)
- `field_name`: The name of the field to search for. [String literal](../syntax#string)
- `json` — The JSON in which the field is searched for. [String](../data-types/string.md#string)
- `field_name` — The name of the field to search for. [String literal](../syntax#string)
**Returned value**
It returns the value of the field as a [`String`](../data-types/string.md#string), including separators if the field exists, or an empty `String` otherwise.
- Returns the value of the field as a string, including separators if the field exists, or an empty string otherwise. [`String`](../data-types/string.md#string)
**Example**
@ -286,6 +308,8 @@ INSERT INTO jsons VALUES ('{"baz":2}');
SELECT simpleJSONExtractRaw(json, 'foo') FROM jsons ORDER BY json;
```
Result:
```response
"-4e3"
@ -294,7 +318,7 @@ SELECT simpleJSONExtractRaw(json, 'foo') FROM jsons ORDER BY json;
{"def":[1,2,3]}
```
## simpleJSONExtractString
### simpleJSONExtractString
Parses `String` in double quotes from the value of the field named `field_name`.
@ -304,14 +328,16 @@ Parses `String` in double quotes from the value of the field named `field_name`.
simpleJSONExtractString(json, field_name)
```
Alias: `visitParamExtractString`.
**Parameters**
- `json`: The JSON in which the field is searched for. [String](../data-types/string.md#string)
- `field_name`: The name of the field to search for. [String literal](../syntax#string)
- `json` — The JSON in which the field is searched for. [String](../data-types/string.md#string)
- `field_name` — The name of the field to search for. [String literal](../syntax#string)
**Returned value**
It returns the value of a field as a [`String`](../data-types/string.md#string), including separators. The value is unescaped. It returns an empty `String`: if the field doesn't contain a double quoted string, if unescaping fails or if the field doesn't exist.
- Returns the unescaped value of a field as a string, including separators. An empty string is returned if the field doesn't contain a double quoted string, if unescaping fails or if the field doesn't exist. [String](../data-types/string.md).
**Implementation details**
@ -336,6 +362,8 @@ INSERT INTO jsons VALUES ('{"foo":"hello}');
SELECT simpleJSONExtractString(json, 'foo') FROM jsons ORDER BY json;
```
Result:
```response
\n\0
@ -343,73 +371,61 @@ SELECT simpleJSONExtractString(json, 'foo') FROM jsons ORDER BY json;
```
## visitParamHas
## JSONExtract functions
This function is [an alias of `simpleJSONHas`](./json-functions#simplejsonhas).
The following functions are based on [simdjson](https://github.com/lemire/simdjson), and designed for more complex JSON parsing requirements.
## visitParamExtractUInt
### isValidJSON
This function is [an alias of `simpleJSONExtractUInt`](./json-functions#simplejsonextractuint).
Checks that passed string is valid JSON.
## visitParamExtractInt
**Syntax**
This function is [an alias of `simpleJSONExtractInt`](./json-functions#simplejsonextractint).
```sql
isValidJSON(json)
```
## visitParamExtractFloat
This function is [an alias of `simpleJSONExtractFloat`](./json-functions#simplejsonextractfloat).
## visitParamExtractBool
This function is [an alias of `simpleJSONExtractBool`](./json-functions#simplejsonextractbool).
## visitParamExtractRaw
This function is [an alias of `simpleJSONExtractRaw`](./json-functions#simplejsonextractraw).
## visitParamExtractString
This function is [an alias of `simpleJSONExtractString`](./json-functions#simplejsonextractstring).
# JSONExtract functions
The following functions are based on [simdjson](https://github.com/lemire/simdjson) designed for more complex JSON parsing requirements.
## isValidJSON(json)
Checks that passed string is a valid json.
Examples:
**Examples**
``` sql
SELECT isValidJSON('{"a": "hello", "b": [-100, 200.0, 300]}') = 1
SELECT isValidJSON('not a json') = 0
```
## JSONHas(json\[, indices_or_keys\]...)
### JSONHas
If the value exists in the JSON document, `1` will be returned.
If the value exists in the JSON document, `1` will be returned. If the value does not exist, `0` will be returned.
If the value does not exist, `0` will be returned.
**Syntax**
Examples:
```sql
JSONHas(json [, indices_or_keys]...)
```
**Parameters**
- `json` — JSON string to parse. [String](../data-types/string.md).
- `indices_or_keys` — A list of zero or more arguments, each of which can be either string or integer. [String](../data-types/string.md), [Int*](../data-types/int-uint.md).
`indices_or_keys` type:
- String = access object member by key.
- Positive integer = access the n-th member/key from the beginning.
- Negative integer = access the n-th member/key from the end.
**Returned value**
- Returns `1` if the value exists in `json`, otherwise `0`. [UInt8](../data-types/int-uint.md).
**Examples**
Query:
``` sql
SELECT JSONHas('{"a": "hello", "b": [-100, 200.0, 300]}', 'b') = 1
SELECT JSONHas('{"a": "hello", "b": [-100, 200.0, 300]}', 'b', 4) = 0
```
`indices_or_keys` is a list of zero or more arguments each of them can be either string or integer.
- String = access object member by key.
- Positive integer = access the n-th member/key from the beginning.
- Negative integer = access the n-th member/key from the end.
Minimum index of the element is 1. Thus the element 0 does not exist.
You may use integers to access both JSON arrays and JSON objects.
So, for example:
The minimum index of the element is 1. Thus the element 0 does not exist. You may use integers to access both JSON arrays and JSON objects. For example:
``` sql
SELECT JSONExtractKey('{"a": "hello", "b": [-100, 200.0, 300]}', 1) = 'a'
@ -419,26 +435,62 @@ SELECT JSONExtractKey('{"a": "hello", "b": [-100, 200.0, 300]}', -2) = 'a'
SELECT JSONExtractString('{"a": "hello", "b": [-100, 200.0, 300]}', 1) = 'hello'
```
## JSONLength(json\[, indices_or_keys\]...)
### JSONLength
Return the length of a JSON array or a JSON object.
Return the length of a JSON array or a JSON object. If the value does not exist or has the wrong type, `0` will be returned.
If the value does not exist or has a wrong type, `0` will be returned.
**Syntax**
Examples:
```sql
JSONLength(json [, indices_or_keys]...)
```
**Parameters**
- `json` — JSON string to parse. [String](../data-types/string.md).
- `indices_or_keys` — A list of zero or more arguments, each of which can be either string or integer. [String](../data-types/string.md), [Int*](../data-types/int-uint.md).
`indices_or_keys` type:
- String = access object member by key.
- Positive integer = access the n-th member/key from the beginning.
- Negative integer = access the n-th member/key from the end.
**Returned value**
- Returns the length of the JSON array or JSON object. Returns `0` if the value does not exist or has the wrong type. [UInt64](../data-types/int-uint.md).
**Examples**
``` sql
SELECT JSONLength('{"a": "hello", "b": [-100, 200.0, 300]}', 'b') = 3
SELECT JSONLength('{"a": "hello", "b": [-100, 200.0, 300]}') = 2
```
## JSONType(json\[, indices_or_keys\]...)
### JSONType
Return the type of a JSON value.
Return the type of a JSON value. If the value does not exist, `Null` will be returned.
If the value does not exist, `Null` will be returned.
**Syntax**
Examples:
```sql
JSONType(json [, indices_or_keys]...)
```
**Parameters**
- `json` — JSON string to parse. [String](../data-types/string.md).
- `indices_or_keys` — A list of zero or more arguments, each of which can be either string or integer. [String](../data-types/string.md), [Int*](../data-types/int-uint.md).
`indices_or_keys` type:
- String = access object member by key.
- Positive integer = access the n-th member/key from the beginning.
- Negative integer = access the n-th member/key from the end.
**Returned value**
- Returns the type of a JSON value as a string, otherwise if the value doesn't exists it returns `Null`. [String](../data-types/string.md).
**Examples**
``` sql
SELECT JSONType('{"a": "hello", "b": [-100, 200.0, 300]}') = 'Object'
@ -446,35 +498,191 @@ SELECT JSONType('{"a": "hello", "b": [-100, 200.0, 300]}', 'a') = 'String'
SELECT JSONType('{"a": "hello", "b": [-100, 200.0, 300]}', 'b') = 'Array'
```
## JSONExtractUInt(json\[, indices_or_keys\]...)
### JSONExtractUInt
## JSONExtractInt(json\[, indices_or_keys\]...)
Parses JSON and extracts a value of UInt type.
## JSONExtractFloat(json\[, indices_or_keys\]...)
**Syntax**
## JSONExtractBool(json\[, indices_or_keys\]...)
Parses a JSON and extract a value. These functions are similar to `visitParam` functions.
If the value does not exist or has a wrong type, `0` will be returned.
Examples:
``` sql
SELECT JSONExtractInt('{"a": "hello", "b": [-100, 200.0, 300]}', 'b', 1) = -100
SELECT JSONExtractFloat('{"a": "hello", "b": [-100, 200.0, 300]}', 'b', 2) = 200.0
SELECT JSONExtractUInt('{"a": "hello", "b": [-100, 200.0, 300]}', 'b', -1) = 300
```sql
JSONExtractUInt(json [, indices_or_keys]...)
```
## JSONExtractString(json\[, indices_or_keys\]...)
**Parameters**
Parses a JSON and extract a string. This function is similar to `visitParamExtractString` functions.
- `json` — JSON string to parse. [String](../data-types/string.md).
- `indices_or_keys` — A list of zero or more arguments, each of which can be either string or integer. [String](../data-types/string.md), [Int*](../data-types/int-uint.md).
If the value does not exist or has a wrong type, an empty string will be returned.
`indices_or_keys` type:
- String = access object member by key.
- Positive integer = access the n-th member/key from the beginning.
- Negative integer = access the n-th member/key from the end.
The value is unescaped. If unescaping failed, it returns an empty string.
**Returned value**
Examples:
- Returns a UInt value if it exists, otherwise it returns `Null`. [UInt64](../data-types/string.md).
**Examples**
Query:
``` sql
SELECT JSONExtractUInt('{"a": "hello", "b": [-100, 200.0, 300]}', 'b', -1) as x, toTypeName(x);
```
Result:
```response
┌───x─┬─toTypeName(x)─┐
│ 300 │ UInt64 │
└─────┴───────────────┘
```
### JSONExtractInt
Parses JSON and extracts a value of Int type.
**Syntax**
```sql
JSONExtractInt(json [, indices_or_keys]...)
```
**Parameters**
- `json` — JSON string to parse. [String](../data-types/string.md).
- `indices_or_keys` — A list of zero or more arguments, each of which can be either string or integer. [String](../data-types/string.md), [Int*](../data-types/int-uint.md).
`indices_or_keys` type:
- String = access object member by key.
- Positive integer = access the n-th member/key from the beginning.
- Negative integer = access the n-th member/key from the end.
**Returned value**
- Returns an Int value if it exists, otherwise it returns `Null`. [Int64](../data-types/int-uint.md).
**Examples**
Query:
``` sql
SELECT JSONExtractInt('{"a": "hello", "b": [-100, 200.0, 300]}', 'b', -1) as x, toTypeName(x);
```
Result:
```response
┌───x─┬─toTypeName(x)─┐
│ 300 │ Int64 │
└─────┴───────────────┘
```
### JSONExtractFloat
Parses JSON and extracts a value of Int type.
**Syntax**
```sql
JSONExtractFloat(json [, indices_or_keys]...)
```
**Parameters**
- `json` — JSON string to parse. [String](../data-types/string.md).
- `indices_or_keys` — A list of zero or more arguments, each of which can be either string or integer. [String](../data-types/string.md), [Int*](../data-types/int-uint.md).
`indices_or_keys` type:
- String = access object member by key.
- Positive integer = access the n-th member/key from the beginning.
- Negative integer = access the n-th member/key from the end.
**Returned value**
- Returns an Float value if it exists, otherwise it returns `Null`. [Float64](../data-types/float.md).
**Examples**
Query:
``` sql
SELECT JSONExtractFloat('{"a": "hello", "b": [-100, 200.0, 300]}', 'b', 2) as x, toTypeName(x);
```
Result:
```response
┌───x─┬─toTypeName(x)─┐
│ 200 │ Float64 │
└─────┴───────────────┘
```
### JSONExtractBool
Parses JSON and extracts a boolean value. If the value does not exist or has a wrong type, `0` will be returned.
**Syntax**
```sql
JSONExtractBool(json\[, indices_or_keys\]...)
```
**Parameters**
- `json` — JSON string to parse. [String](../data-types/string.md).
- `indices_or_keys` — A list of zero or more arguments, each of which can be either string or integer. [String](../data-types/string.md), [Int*](../data-types/int-uint.md).
`indices_or_keys` type:
- String = access object member by key.
- Positive integer = access the n-th member/key from the beginning.
- Negative integer = access the n-th member/key from the end.
**Returned value**
- Returns a Boolean value if it exists, otherwise it returns `0`. [Bool](../data-types/boolean.md).
**Example**
Query:
``` sql
SELECT JSONExtractBool('{"passed": true}', 'passed');
```
Result:
```response
┌─JSONExtractBool('{"passed": true}', 'passed')─┐
│ 1 │
└───────────────────────────────────────────────┘
```
### JSONExtractString
Parses JSON and extracts a string. This function is similar to [`visitParamExtractString`](#simplejsonextractstring) functions. If the value does not exist or has a wrong type, an empty string will be returned.
**Syntax**
```sql
JSONExtractString(json [, indices_or_keys]...)
```
**Parameters**
- `json` — JSON string to parse. [String](../data-types/string.md).
- `indices_or_keys` — A list of zero or more arguments, each of which can be either string or integer. [String](../data-types/string.md), [Int*](../data-types/int-uint.md).
`indices_or_keys` type:
- String = access object member by key.
- Positive integer = access the n-th member/key from the beginning.
- Negative integer = access the n-th member/key from the end.
**Returned value**
- Returns an unescaped string from `json`. If unescaping failed, if the value does not exist or if it has a wrong type then it returns an empty string. [String](../data-types/string.md).
**Examples**
``` sql
SELECT JSONExtractString('{"a": "hello", "b": [-100, 200.0, 300]}', 'a') = 'hello'
@ -484,16 +692,35 @@ SELECT JSONExtractString('{"abc":"\\u263"}', 'abc') = ''
SELECT JSONExtractString('{"abc":"hello}', 'abc') = ''
```
## JSONExtract(json\[, indices_or_keys...\], Return_type)
### JSONExtract
Parses a JSON and extract a value of the given ClickHouse data type.
Parses JSON and extracts a value of the given ClickHouse data type. This function is a generalized version of the previous `JSONExtract<type>` functions. Meaning:
This is a generalization of the previous `JSONExtract<type>` functions.
This means
`JSONExtract(..., 'String')` returns exactly the same as `JSONExtractString()`,
`JSONExtract(..., 'Float64')` returns exactly the same as `JSONExtractFloat()`.
Examples:
**Syntax**
```sql
JSONExtract(json [, indices_or_keys...], return_type)
```
**Parameters**
- `json` — JSON string to parse. [String](../data-types/string.md).
- `indices_or_keys` — A list of zero or more arguments, each of which can be either string or integer. [String](../data-types/string.md), [Int*](../data-types/int-uint.md).
- `return_type` — A string specifying the type of the value to extract. [String](../data-types/string.md).
`indices_or_keys` type:
- String = access object member by key.
- Positive integer = access the n-th member/key from the beginning.
- Negative integer = access the n-th member/key from the end.
**Returned value**
- Returns a value if it exists of the specified return type, otherwise it returns `0`, `Null`, or an empty-string depending on the specified return type. [UInt64](../data-types/int-uint.md), [Int64](../data-types/int-uint.md), [Float64](../data-types/float.md), [Bool](../data-types/boolean.md) or [String](../data-types/string.md).
**Examples**
``` sql
SELECT JSONExtract('{"a": "hello", "b": [-100, 200.0, 300]}', 'Tuple(String, Array(Float64))') = ('hello',[-100,200,300])
@ -506,17 +733,38 @@ SELECT JSONExtract('{"day": "Thursday"}', 'day', 'Enum8(\'Sunday\' = 0, \'Monday
SELECT JSONExtract('{"day": 5}', 'day', 'Enum8(\'Sunday\' = 0, \'Monday\' = 1, \'Tuesday\' = 2, \'Wednesday\' = 3, \'Thursday\' = 4, \'Friday\' = 5, \'Saturday\' = 6)') = 'Friday'
```
## JSONExtractKeysAndValues(json\[, indices_or_keys...\], Value_type)
### JSONExtractKeysAndValues
Parses key-value pairs from a JSON where the values are of the given ClickHouse data type.
Parses key-value pairs from JSON where the values are of the given ClickHouse data type.
Example:
**Syntax**
```sql
JSONExtractKeysAndValues(json [, indices_or_keys...], value_type)
```
**Parameters**
- `json` — JSON string to parse. [String](../data-types/string.md).
- `indices_or_keys` — A list of zero or more arguments, each of which can be either string or integer. [String](../data-types/string.md), [Int*](../data-types/int-uint.md).
- `value_type` — A string specifying the type of the value to extract. [String](../data-types/string.md).
`indices_or_keys` type:
- String = access object member by key.
- Positive integer = access the n-th member/key from the beginning.
- Negative integer = access the n-th member/key from the end.
**Returned value**
- Returns an array of parsed key-value pairs. [Array](../data-types/array.md)([Tuple](../data-types/tuple.md)(`value_type`)).
**Example**
``` sql
SELECT JSONExtractKeysAndValues('{"x": {"a": 5, "b": 7, "c": 11}}', 'x', 'Int8') = [('a',5),('b',7),('c',11)];
```
## JSONExtractKeys
### JSONExtractKeys
Parses a JSON string and extracts the keys.
@ -526,14 +774,14 @@ Parses a JSON string and extracts the keys.
JSONExtractKeys(json[, a, b, c...])
```
**Arguments**
**Parameters**
- `json` — [String](../data-types/string.md) with valid JSON.
- `a, b, c...` — Comma-separated indices or keys that specify the path to the inner field in a nested JSON object. Each argument can be either a [String](../data-types/string.md) to get the field by the key or an [Integer](../data-types/int-uint.md) to get the N-th field (indexed from 1, negative integers count from the end). If not set, the whole JSON is parsed as the top-level object. Optional parameter.
**Returned value**
Array with the keys of the JSON. [Array](../data-types/array.md)([String](../data-types/string.md)).
- Returns an array with the keys of the JSON. [Array](../data-types/array.md)([String](../data-types/string.md)).
**Example**
@ -552,31 +800,67 @@ text
└────────────────────────────────────────────────────────────┘
```
## JSONExtractRaw(json\[, indices_or_keys\]...)
### JSONExtractRaw
Returns a part of JSON as unparsed string.
Returns part of the JSON as an unparsed string. If the part does not exist or has the wrong type, an empty string will be returned.
If the part does not exist or has a wrong type, an empty string will be returned.
**Syntax**
Example:
```sql
JSONExtractRaw(json [, indices_or_keys]...)
```
**Parameters**
- `json` — JSON string to parse. [String](../data-types/string.md).
- `indices_or_keys` — A list of zero or more arguments, each of which can be either string or integer. [String](../data-types/string.md), [Int*](../data-types/int-uint.md).
`indices_or_keys` type:
- String = access object member by key.
- Positive integer = access the n-th member/key from the beginning.
- Negative integer = access the n-th member/key from the end.
**Returned value**
- Returns part of the JSON as an unparsed string. If the part does not exist or has the wrong type, an empty string is returned. [String](../data-types/string.md).
**Example**
``` sql
SELECT JSONExtractRaw('{"a": "hello", "b": [-100, 200.0, 300]}', 'b') = '[-100, 200.0, 300]';
```
## JSONExtractArrayRaw(json\[, indices_or_keys...\])
### JSONExtractArrayRaw
Returns an array with elements of JSON array, each represented as unparsed string.
Returns an array with elements of JSON array, each represented as unparsed string. If the part does not exist or isn’t an array, then an empty array will be returned.
If the part does not exist or isn’t array, an empty array will be returned.
**Syntax**
Example:
```sql
JSONExtractArrayRaw(json [, indices_or_keys...])
```
``` sql
**Parameters**
- `json` — JSON string to parse. [String](../data-types/string.md).
- `indices_or_keys` — A list of zero or more arguments, each of which can be either string or integer. [String](../data-types/string.md), [Int*](../data-types/int-uint.md).
`indices_or_keys` type:
- String = access object member by key.
- Positive integer = access the n-th member/key from the beginning.
- Negative integer = access the n-th member/key from the end.
**Returned value**
- Returns an array with elements of JSON array, each represented as unparsed string. Otherwise, an empty array is returned if the part does not exist or is not an array. [Array](../data-types/array.md)([String](../data-types/string.md)).
**Example**
```sql
SELECT JSONExtractArrayRaw('{"a": "hello", "b": [-100, 200.0, "hello"]}', 'b') = ['-100', '200.0', '"hello"'];
```
## JSONExtractKeysAndValuesRaw
### JSONExtractKeysAndValuesRaw
Extracts raw data from a JSON object.
@ -640,13 +924,30 @@ Result:
└───────────────────────────────────────────────────────────────────────────────────────────────────────┘
```
## JSON_EXISTS(json, path)
### JSON_EXISTS
If the value exists in the JSON document, `1` will be returned.
If the value exists in the JSON document, `1` will be returned. If the value does not exist, `0` will be returned.
If the value does not exist, `0` will be returned.
**Syntax**
Examples:
```sql
JSON_EXISTS(json, path)
```
**Parameters**
- `json` — A string with valid JSON. [String](../data-types/string.md).
- `path` — A string representing the path. [String](../data-types/string.md).
:::note
Before version 21.11 the order of arguments was wrong, i.e. JSON_EXISTS(path, json)
:::
**Returned value**
- Returns `1` if the value exists in the JSON document, otherwise `0`.
**Examples**
``` sql
SELECT JSON_EXISTS('{"hello":1}', '$.hello');
@ -655,17 +956,32 @@ SELECT JSON_EXISTS('{"hello":["world"]}', '$.hello[*]');
SELECT JSON_EXISTS('{"hello":["world"]}', '$.hello[0]');
```
### JSON_QUERY
Parses a JSON and extract a value as a JSON array or JSON object. If the value does not exist, an empty string will be returned.
**Syntax**
```sql
JSON_QUERY(json, path)
```
**Parameters**
- `json` — A string with valid JSON. [String](../data-types/string.md).
- `path` — A string representing the path. [String](../data-types/string.md).
:::note
Before version 21.11 the order of arguments was wrong, i.e. JSON_EXISTS(path, json)
:::
## JSON_QUERY(json, path)
**Returned value**
Parses a JSON and extract a value as JSON array or JSON object.
- Returns the extracted value as a JSON array or JSON object. Otherwise it returns an empty string if the value does not exist. [String](../data-types/string.md).
If the value does not exist, an empty string will be returned.
**Example**
Example:
Query:
``` sql
SELECT JSON_QUERY('{"hello":"world"}', '$.hello');
@ -682,17 +998,38 @@ Result:
[2]
String
```
### JSON_VALUE
Parses a JSON and extract a value as a JSON scalar. If the value does not exist, an empty string will be returned by default.
This function is controlled by the following settings:
- by SET `function_json_value_return_type_allow_nullable` = `true`, `NULL` will be returned. If the value is complex type (such as: struct, array, map), an empty string will be returned by default.
- by SET `function_json_value_return_type_allow_complex` = `true`, the complex value will be returned.
**Syntax**
```sql
JSON_VALUE(json, path)
```
**Parameters**
- `json` — A string with valid JSON. [String](../data-types/string.md).
- `path` — A string representing the path. [String](../data-types/string.md).
:::note
Before version 21.11 the order of arguments was wrong, i.e. JSON_QUERY(path, json)
Before version 21.11 the order of arguments was wrong, i.e. JSON_EXISTS(path, json)
:::
## JSON_VALUE(json, path)
**Returned value**
Parses a JSON and extract a value as JSON scalar.
- Returns the extracted value as a JSON scalar if it exists, otherwise an empty string is returned. [String](../data-types/string.md).
If the value does not exist, an empty string will be returned by default, and by SET `function_json_value_return_type_allow_nullable` = `true`, `NULL` will be returned. If the value is complex type (such as: struct, array, map), an empty string will be returned by default, and by SET `function_json_value_return_type_allow_complex` = `true`, the complex value will be returned.
**Example**
Example:
Query:
``` sql
SELECT JSON_VALUE('{"hello":"world"}', '$.hello');
@ -712,11 +1049,7 @@ world
String
```
:::note
Before version 21.11 the order of arguments was wrong, i.e. JSON_VALUE(path, json)
:::
## toJSONString
### toJSONString
Serializes a value to its JSON representation. Various data types and nested structures are supported.
64-bit [integers](../data-types/int-uint.md) or bigger (like `UInt64` or `Int128`) are enclosed in quotes by default. [output_format_json_quote_64bit_integers](../../operations/settings/settings.md#session_settings-output_format_json_quote_64bit_integers) controls this behavior.
@ -762,7 +1095,7 @@ Result:
- [output_format_json_quote_denormals](../../operations/settings/settings.md#settings-output_format_json_quote_denormals)
## JSONArrayLength
### JSONArrayLength
Returns the number of elements in the outermost JSON array. The function returns NULL if input JSON string is invalid.
@ -795,7 +1128,7 @@ SELECT
```
## jsonMergePatch
### jsonMergePatch
Returns the merged JSON object string which is formed by merging multiple JSON objects.